Ferris Bueller's Day Off

User Cool Papa Bell on Metatalk sums the theory up well:

My favorite thought-piece about Ferris Bueller is the “Fight Club” theory, in which Ferris Bueller, the person, is just a figment of Cameron’s imagination, like Tyler Durden, and Sloane is the girl Cameron secretly loves.

One day while he’s lying sick in bed, Cameron lets “Ferris” steal his father’s car and take the day off, and as Cameron wanders around the city, all of his interactions with Ferris and Sloane, and all the impossible hijinks, are all just played out in his head. This is part of the reason why the “three” characters can see so much of Chicago in less than one day — Cameron is alone, just imagining it all.

It isn’t until he destroys the front of the car in a fugue state does he finally get a grip and decide to confront his father, after which he imagines a final, impossible escape for Ferris and a storybook happy ending for Sloane (”He’s gonna marry me!”), the girl that Cameron knows he can never have.

I loved this theory. Cameron is such a great character and the idea of him running around the streets of Chicago  talking to himself all day is a bit dark but it's also amazing. It gives Cameron's arc in the film so much weight, especially the scene where Cameron stares at a painting of Monet and as he looks closer and closer the faces stop being recognizable and look increasingly chaotic. 
Check out this recut trailer by  Classy Hands.

Bueller?
18" by 24"
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